The purpose of this study is to investigate safety and effectiveness of non-operative transcatheter closure of isolated patent ductus arteriosus (PDA) and atrial septal defect (ASD). The device consists of an occluder, counter-occluder and a delivery system and is implanted across the defect via seven or eight French catheters. Effectiveness will be determined by echo-Doppler studies at follow-up. If transcatheter closure is shown to be effective and safe, it can be recommended as a procedure of choice to close PDA and ASD.